I bought a Toto single piece toilet that has a base that is covered. It's only two years old and the valve is leaking and my husband is trying to replace the whole valve assembly. We can not unthread the plastic nut that holds the valve assembly in the tank. It appears to be torqued too tight. My husband blames me for buying a fancy toilet and I am quite frankly feed up at his DIY skills. He bought a special wrench to clamp onto the plastic nut but because of the design, it is too long to clamp on to the nut. He will pull the whole toilet out today. Any advice on how to remove this nut and save the hassle of a whole toilet removal?